From dbc02ed889e4d4e5340d05baf85058edd6f4b7f8 Mon Sep 17 00:00:00 2001
From: Axel Huebl <axel.huebl@plasma.ninja>
Date: Mon, 18 Aug 2025 12:47:46 -0700
Subject: [PATCH] AMReX Enum: Underlying Value

Sometimes one needs the underlying (u)int type of an enum,
e.g., when building bitmasks. This adds a helper function to
`AMREX_ENUM`.
---
 Src/Base/AMReX_Enum.H | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Src/Base/AMReX_Enum.H b/Src/Base/AMReX_Enum.H
index b94e30d396e..5c6525e9ffd 100644
--- a/Src/Base/AMReX_Enum.H
+++ b/Src/Base/AMReX_Enum.H
@@ -128,6 +128,17 @@ namespace amrex
     {
         return std::string(ET::class_name);
     }
+
+    /** Return the underlying (u)int of an enum value
+     *
+     * Useful when building bitmasks.
+     */
+    template <typename T, typename ET = amrex_enum_traits<T>,
+              std::enable_if_t<ET::value,int> = 0>
+    constexpr auto getEnumUnderlyingValue (T v) noexcept
+    {
+        return static_cast<std::underlying_type_t<T>>(v);
+    }
 }
 
 #define AMREX_ENUM(CLASS, ...) \